Method of manufacturing a piston

ABSTRACT

An improved method of manufacturing a piston is provided. The piston includes a substantially cylindrical member having a first end and a second end. The cylindrical member includes an open cavity extending axially from the second end to adjacent the first end such that the second end has an inner annular surface defined by an inner diameter. The piston further includes a disk having a radially outer surface defined by an outer diameter fixedly secured to the second end of the cylindrical member. The outer diameter of the disk is substantially equal to the inner diameter of the inner annular surface of the second end of the cylindrical member. A circumferentially extending recessed area for receiving particles produced while fixedly securing the disk to the second end of the cylindrical member is provided on either the radially outer surface of the disk or the inner annular surface of the second end of the cylindrical member.

This is a Divisional of U.S. application Ser. No. 08/299,726, filed Sep.1, 1994.

FIELD OF THE INVENTION

This invention relates to a piston and a method for manufacturing thesame.

BACKGROUND ART

Pistons which are adapted for use in hydraulic pumps and motors aresubject to significant stress levels and high velocities, as the pistonstranslate and rotate within a cylinder block. In order to withstand sucha harsh operating environment, they should be constructed from a strongwear resistant material, but simultaneously not hinder performance withexcess weight. Therefore, a hollowed section may be provided in thepiston, as disclosed by Havens in U.S. Pat. No. 3,319,575, for example.

However, often in the construction of pistons with hollowed sections,excess particles from the process of joining the various segmentstogether may settle within the hollowed section. This poses asignificant problem as the undesirable particles wear on the inner wallsof the piston during operation within the cylinder block, andsubsequently contaminate the piston structure. Continual translationaland rotational motion may trigger failure of one of the pistons, andeventually cause malfunctioning of the hydraulic unit.

The problems of weld particles within a piston chamber used in internalcombustion engines is recognized in a patent to Kohl et al., U.S. Pat.No. 3,319,536. Kohl et al. discloses the use of annular rings spacedfrom the piston chamber into which the ends of charged particle beamsextend, so that if the welded seams created from the charged particlebeams tear, the tear will follow the contour of the rings. While Kohl etal. seeks to overcome the problem of excess weld particles by providinga extrinsic element, it does not, as the invention to be described morefully hereinafter, teach providing a circumferentially extendingrecessed area within the piston structure to receive and containparticles produced while constructing the piston.

The present invention is directed to overcoming the above-referencedproblems.

SUMMARY OF THE INVENTION

More specifically, this invention relates to a piston and a method ofmanufacturing the same. The piston includes a substantially cylindricalmember having a first end and a second end. The cylindrical memberincludes an open cavity extending axially from the second end toadjacent the first end such that the second end has an inner annularsurface defined by an inner diameter. The piston further includes a diskhaving a radially outer surface defined by an outer diameter fixedlysecured to the second end of the cylindrical member. The outer diameterof the disk is substantially equal to the inner diameter of the innerannular surface of the second end of the cylindrical member. Theradially outer surface of the disk includes a circumferentiallyextending recessed area for receiving particles produced while fixedlysecuring the disk to the second end of the cylindrical member.

It is therefore a primary object of the invention to provide a method ofmanufacturing a piston which prevents particles from entering a cavityof a cylindrical member while fixedly securing a disk to a second end ofthe cylindrical member.

It is a further object of the invention to provide a method ofmanufacturing a piston which receives and contains particles producedfrom fixedly securing an annular cylindrical member to an elongatedmember within first and second circumferentially extending recessedareas.

Another feature of the invention is to provide the cylindrical member asan integral element.

Yet another feature of one embodiment of the invention is to provide amethod of manufacturing a piston which includes providing asubstantially cylindrical member having a first end and a second end andforming an open cavity in the cylindrical member extending axially fromthe second end to adjacent the first end such that the second end has aninner annular surface defined by an inner diameter. The method alsoincludes providing a disk having a radially outer surface defined by anouter diameter substantially equal to the inner diameter of the innerannular surface of the second end of the cylindrical member. The methodfurther includes forming a circumferentially extending recessed areaeither in the radially outer surface of the disk or in the inner annularsurface of the second end of the cylindrical member, and welding orbrazing the disk to the second end of the cylindrical member by weldingor brazing to the recessed area of the radially outer surface of thedisk such that particles produced while welding or brazing the disk tothe second end of the cylindrical member are received and containedwithin the recessed area.

Another feature of the invention is to provide in the step of weldingthe disk to the second end of the cylindrical member, the step ofselecting a form of welding from the group of electron beam welding,laser beam welding or arc welding to weld the disk to the second end ofthe cylindrical member.

A feature of a further embodiment of the invention is to provide amethod of manufacturing a piston which includes providing an elongatedmember having a first radially outwardly extending cylindricalprojection with a first radially outer surface defined by a first outerdiameter at a first end of the elongated member and a second radiallyoutwardly extending cylindrical projection with a second radially outersurface defined by a second outer diameter substantially equal to thefirst outer diameter at a second end of the elongated member. The methodalso includes providing an annular cylindrical member having an innerannular surface defined by an inner diameter substantially equal to thefirst and second outer diameters of the first and second radially outersurfaces of the first and second projections of the elongated member.The method further includes forming a first circumferentially extendingrecessed area in the first radially outer surface of the firstprojection of the elongated member and forming a secondcircumferentially extending recessed area in the second radially outersurface of the second projection of the elongated member. The methodcontinues by welding the annular cylindrical member to the first andsecond projections of the elongated member by welding to the first andsecond recessed areas of the first and second radially outer surfaces ofthe first and second projections of the elongated member such thatparticles produced while welding the annular cylindrical member to thefirst and second projections of the elongated member are received andcontained with the first and second recessed areas.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the organization, the advantages, and further objects of the inventionmay be readily ascertained by one skilled in the art from the followingdetailed description when read in conjunction with the accompanyingdrawings in which:

FIG. 1 is a cross-sectional view of a piston illustrating an embodimentof the instant invention;

FIG. 2 is a cross-sectional view along the line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view of a piston illustrating a furtherembodiment of the instant invention;

FIG. 4 is a cross-sectional view of a piston illustrating a furtherembodiment of the instant invention;

FIG. 5 is a cross-sectional view of a piston illustrating a furtherembodiment of the instant invention;

FIG. 6 is a process flow diagram of an embodiment of a method ofmanufacturing a piston in accordance with the instant invention; and

FIG. 7 is a process flow diagram of a further embodiment of a method ofmanufacturing a piston in accordance with the instant invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and specifically FIG. 1, a piston,generally designated 10, is illustrated in accordance with the instantinvention. The piston 10 is formed of a substantially cylindrical member12 having a first end, generally designated 14, and a second end,generally designated 16. The cylindrical member 12 has an open cavity 18which extends axially from the second end 16 to adjacent the first end14. From such a geometry, it may be appreciated that the second end 16is annular in nature and has an inner annular surface 20 which isdefined by an inner diameter, D₁. Further, the open cavity 18 extendingfrom the second end 16 of the cylindrical member 12 may be annularlyshaped such that the second end 16 includes an inner elongated portion24. With this geometry, one skilled in the art can appreciate that theinner elongated portion 24 has a radially outer surface 26 which isdefined by an outer diameter, D₂, which is concentrically located withinthe inner annular surface 20. The cavity 18 allows for a reduction inmass and subsequent weight of the piston 10 which results in increasedperformance. The first end 14 of the cylindrical member 12 may bedefined as a generally spherical projection 30 which enables the firstend 14 of the piston 10 to reciprocate in a translating and rotatingmotion within a fluidics unit (not shown), such as a hydraulic pump ormotor. Furthermore, the inner elongated portion 24 of the second end 16of the cylindrical member 12 may include a passage 32 which extendsaxially from the second end 16 through the spherical projection 30 ofthe first end 14 of the cylindrical member 12. The passage 32 allowslubricating fluid to flow between the spherical projection 30 and thefluidics unit (not shown).

The cylindrical member 12, in a preferred embodiment, may be constructedas an integral element through a manufacturing process such as thatknown in the art as trepanning or gun drilling. Alternatively, thecylindrical member 12 may be constructed by forging, extruding, coldforming, casting, electro-chemical machining (ECM) or electricaldischarge machining (EDM) the cylindrical member 12. By utilizing such aconstruction, any joint likely to trigger failure from uncontrolledstress is eliminated from the spherical projection 30 of the first end14 and relocated to the second end 16 of the cylindrical member 12.Furthermore, constructing the cylindrical member 12 as an integralelement eases inspection, especially that of a non-destructive naturebecause only one end of hardware needs to be inspected. In a preferredembodiment, the cylindrical member 12 should be constructed from a wearresistant material, such as a bearing steel, case hardening steel or ananodized aluminum, or as the art advances, may be constructed from aceramic or other non-metallic material.

The piston 10 also includes a disk 34 which has a radially outer surface36 which is defined by an outer diameter, D₃ (FIG. 2). The disk 34 maybe manufactured from any one several materials such as bearing steel,carburizing steel, stainless steel, carbon steel, nickel or nickel-basedsuper alloy, or a ceramic or non-metallic material compatible with thecylindrical member 12. The outer diameter D₃ of the disk 34 issubstantially equal to the inner diameter D₁ of the inner annularsurface 20 of the second end 16 of the cylindrical member 12. As can beseen in FIG. 1, the radially outer surface 36 of the disk 34 includes acircumferentially extending recessed area 40. The recessed area 40 maybe in the form of a groove or channel, as shown, or as can beappreciated, another form of corrugation.

In assembling the piston 10, the disk 34 is fixedly secured to thecylindrical member 12 by a manufacturing process such as welding orbrazing. As can be appreciated from one skilled in the art, the recessedarea 40 of the radially outer surface 36 of the disk 34 receivesparticles produced from the welding or brazing process used to fixedlysecure the disk 34 to the second end 16 of the cylindrical member 12,and prevents such particles from entering the cavity 18 of the piston10. Thus, the subsequent failure of the piston 10 within the fluidicsunit because of excess weld particles translating and rotating withinthe piston 10 and wearing down the inner annular surface 20 of thecylindrical member 12 is minimized by providing the recessed area 40.

As can be viewed in FIG. 2, the disk 34 is preferably in the form of anannular ring 42 which has a central opening 44 therethrough. With such ageometry, it can be appreciated that the annular ring 42 has a radiallyinner surface 46 which is defined by an inner diameter, D₄, about theopening 44. The inner diameter D₄ of the annular ring 42 issubstantially equal to the outer diameter D₂ of the inner elongatedportion 24 of the second end 16 of the cylindrical member 12. Theradially inner surface 46 of the annular ring 42 may also include asecond circumferentially recessed area 50 (FIG. 1) for receiving weldparticles produced in the process of fixedly securing the annular ring42 to the second end 16 of the cylindrical member 12.

As can be appreciated from FIGS. 1 and 2, when the disk 34 is in theform of the annular ring 42, the piston 10 includes a firstcircumferential weld 52 fixedly securing the radially inner surface 46of the annular ring 42 to the radially outer surface 26 of the innerelongated portion 24 of the second end 16 of the cylindrical member 12.The piston 10 also includes a second circumferential weld 54 whichfixedly secures the radially outer surface 36 of the annular ring 42 tothe inner annular surface 20 of the second end 16 of the cylindricalmember 12. As can be appreciated in this embodiment, both the recessedarea 40 and the second recessed area 50 receive particles produced fromthe second and first circumferential welds, respectively, as the annularring 42 is fixedly secured to the second end 16 of the cylindricalmember 12.

FIG. 3 depicts a further embodiment of a piston 310 in accordance withthe instant invention. In this embodiment, an inner annular surface 320of a second end 316 of a cylindrical member 312 includes acircumferentially extending recessed area 356. The recessed area 356 isadapted to receive weld particles produced while fixedly securing aradially outer surface 336 of a disk 334 to the inner annular surface320 of the second end 316 of the cylindrical member 312 in a similarfashion to the recessed area 40 of the embodiment depicted in FIG. 1. Aradially outer surface 326 of an inner elongated portion 324 of thesecond end 316 of the cylindrical member 312 may also include a secondcircumferentially extending recessed area 358 for receiving andcontaining particles produced while fixedly securing a radially innersurface 346 of the disk 334, when the disk 334 is in the form of anannular ring, to the radially outer surface 326 of the inner elongatedportion 324 of the second end 316 of the cylindrical member 312 throughsuch manufacturing processes as welding and brazing. One skilled in theart can appreciate the features of piston 10 for the embodiment shown inFIG. 1 are apparent with the alternative embodiment disclosed in FIG. 3.

Referring now to FIG. 6, a process flow diagram of a method ofmanufacturing a piston, as disclosed above, is illustrated in accordancewith the instant invention.

A first step 70 of the process includes providing the substantiallycylindrical member 12 having the first end 14 and the second end 16(FIG. 1). A second step 72 of the process includes forming the opencavity 18 in the cylindrical member 12 which extends axially from thesecond end 16 to adjacent the first end 14 of the cylindrical member 12.One skilled in the art can appreciate by forming the cavity 18 with sucha geometry, the second end 16 of the cylindrical member includes theinner annular surface 20 which is defined by the inner diameter, D₁(FIG. 1).

The method continues by providing, in a third step 74, the disk 34having the radially outer surface 36 defined by the outer diameter, D₃(FIG. 1), which is substantially equal to the inner diameter D₁ of theinner annular surface 20 of the second end 16 of the cylindrical member12.

The method continues by allowing alternative embodiments of the piston10 to be manufactured either via a step 76 or an alternate step 78. Thestep 76 includes forming the circumferentially extending recessed area40 in the radially outer surface 36 of the disk 34 (FIG. 1). Thealternate step 78 includes forming the circumferentially extendingrecessed area 356 in the inner annular surface 320 of the second end 316of the cylindrical member 312 (FIG. 3). Additionally, one skilled in theart can appreciate that if the disk 34 is provided in the form of theannular ring 42 (FIG. 2), the step 76 includes forming the secondcircumferentially extending recessed area 50 in the radially innersurface 46 of the annular ring 42. In the alternative embodimentdisclosed (FIG. 3), the alternate step 78 includes forming the secondcircumferentially extending recessed area 358 in the radially outersurface 326 of the inner elongated portion 324 of the second end 316 ofthe cylindrical member 312.

As illustrated in FIG. 6, the process concludes in either a final step80 or a final alternate step 82. In the final step 80, the disk 34 iswelded to the second end 16 of the cylindrical member 12 by welding toeither of the recessed areas 40 or 356, formed in the step 76 or thealternate step 78, respectively, depending on which embodiment isemployed. By limiting penetration of welding to either of the recessedareas 40 and 356, formed either in the steps 76 and 78, respectively,any particles produced while welding the disk 34 to the second end 16 ofthe cylindrical member 12 are received and contained within either ofthe recessed areas 40 and 356, and subsequently prevented from enteringthe cavity 18. Additionally, if the disk 34 is provided in the form ofthe annular ring 42 (FIG. 2), the annular ring 42 is also welded to thesecond end 16 of the cylindrical member 12 by welding to the secondrecessed area 50 in the radially inner surface 46 of the annular ring 42for the embodiment disclosed in FIG. 1, and to the second recessed area358 in the radially outer surface 326 of the inner elongated portion 324of the second end 316 of the cylindrical member 312 for the embodimentdisclosed in FIG. 3.

In the final step 80, several welding alternatives may be utilized toweld the disk 34 to the second end 16 of the cylindrical member 12.These include electron beam welding, laser beam welding and arc welding,as for example, in the form of tungsten inert gas welding or plasma arcwelding.

In a further embodiment of the method disclosed in FIG. 6, the finalalternate step 82 includes brazing the disk 34 to the second end 16 ofthe cylindrical member 12 by brazing to either of the recessed areas 40or 356, formed in the step 76 or the alternate step 78, respectively,depending on which embodiment of the piston 10 or the piston 310 isemployed. One skilled in the art of manufacturing pistons can appreciatethat brazing may include low temperature soldering. Each of thesemanufacturing alternatives bear advantages depending on the materialselected from which to construct the disk 34 and the cylindrical member12.

Referring now to FIG. 4, an alternate preferred embodiment of a piston402 is disclosed in accordance with the instant invention. The piston402 is formed of an elongated member 404 having a first end, generallydesignated 406, and a second end, generally designated 408. Theelongated member 404 includes a first radially outwardly extendingcylindrical projection 410 at the first end 406 of the elongated member404, and a second radially outwardly extending cylindrical projection412 at the second end 408 of the elongated member 404. With such ageometry, one skilled in the art can appreciate that the firstprojection 410 has a first radially outer surface 414 which is definedby a first outer diameter, D₅. The second projection 412 has a secondradially outer surface 416 which is defined by a second outer diameter,D₆. In a preferred embodiment, one can appreciate the first outerdiameter D₅ of the first radially outer surface 414 of the firstprojection 410 is substantially equal to the second outer diameter D₆ ofthe second radially outer surface 416 of the second projection 412. Thefirst end 406 of the elongated member 404 may be defined as a generallyspherical projection 418 which enables the first end 406 of the piston402 to reciprocate in a translating and rotating motion within afluidics unit (not shown), such as a hydraulic pump or motor.Furthermore, the elongated member 404 may include a passage whichextends axially from the second end 408 through the spherical projection418 of the first end 406 of the elongated member 404. The passage 420allows lubricating fluid to flow between the spherical projection 418and the fluidics unit (not shown).

The elongated member 404, in a preferred embodiment, may be constructedas an integral element through a manufacturing process such as thatknown in the art as lathe turning. Alternatively, the elongated member404 may be constructed by utilizing the manufacturing processes of gundrilling, forging, extruding, cold forming, casting, electro-chemicalmachining (ECM) or electrical discharge machining (EDM). In a preferredembodiment, the elongated member 404 should be constructed from a wearresistant material, such as a bearing steel, case hardening steel or ananodized aluminum, or as the art advances, may be constructed from aceramic or other non-metallic material.

As can be seen in FIG. 4, the first radially outer surface 414 of thefirst projection 410 includes a first circumferentially extendingrecessed area 426 and the second radially outer surface 416 of thesecond projection 412 includes a second circumferentially extendingrecessed area 428. The first and second recessed areas, 426 and 428, maybe in the form of a groove or channel, as shown, or as can beappreciated, another form of corrugation.

The piston 402 also includes an annular cylindrical member 422 which hasan inner annular surface 424 which is defined by an inner diameter, D₇.The annular cylindrical member 422 may be manufactured from any oneseveral materials such as bearing steel, carburizing steel, stainlesssteel, carbon steel, nickel or nickel-based super alloy, or a ceramic ornon-metallic material compatible with the elongated member 404. One canappreciate that the inner diameter D₇ of the inner annular surface 424of the annular cylindrical member 422 is substantially equal to thefirst outer diameter D₅ and the second outer diameter D₆ of the firstand second radially outer surfaces, 414 and 416, respectively, of theelongated member 404.

In assembling the piston 402, the annular cylindrical member 422 isfixedly secured to the first projection 410 and the second projection412 of the elongated member 404. With this geometry, a hollow cavity 430is formed between the annular cylindrical member 422 and the elongatedmember 404. The cavity 430 allows for a reduction in mass and subsequentweight of the piston 402 which results in increased performance. As canbe appreciated from on skilled in the art, the first and second recessedareas, 426 and 428, of the first and second radially outer surfaces, 414and 416, of the first and second projections, 410 and 412, respectively,of the elongated member 404 receive particles produced from a weldingprocess used to fixedly secure the annular cylindrical member 422 to theelongated member 404, and prevent such particles from entering thecavity 430 of the piston 402. A brazing process may also be employed tofixedly secure the annular cylindrical member 422 to the first andsecond projections, 410 and 412 of the elongated member 404 whereinexcess brazing material is received and contained within the first andsecond recessed areas, 426 and 428 of the first and second projections,410 and 412 of the elongated member 404. Thus, the subsequent failure ofthe piston 402 within a fluidics unit because of either undesirable weldparticles or excess brazing material translating and rotating within thecavity 430 of the piston 402 and wearing down the inner annular surface424 of the annular cylindrical member 422 is minimized by providing thefirst and second recessed areas, 426 and 428.

As can be appreciated from FIG. 4, when the manufacturing process ofwelding is utilized to fixedly secure the first and second projections410 of the elongated member 404 to the annular cylindrical member 422,the piston 402 includes a first circumferential weld 432 fixedlysecuring the first radially outer surface 414 of the first projection410 of the elongated member 404 to the inner annular surface 424 of theannular cylindrical member 422. The piston 402 also includes a secondcircumferential weld 434 which fixedly secures the second radially outersurface 416 of the second projection 412 of the elongated member 404 tothe inner annular surface 424 of the annular cylindrical member 422.

FIG. 5 depicts a further embodiment of a piston 502 in accordance withthe instant invention. In this embodiment, an inner annular surface 524of an annular cylindrical member 522 includes a first circumferentiallyextending recessed area 550 opposite a first radially outwardlyextending cylindrical projection 510 of an elongated member 504. Theinner annular surface 524 of the annular cylindrical member 522 alsoincludes a second circumferentially extending recessed area 552 oppositea second radially outwardly extending cylindrical projection 512 of theelongated member 504. The first and second recessed areas, 550 and 552are adapted to receive weld particles produced while fixedly securingthe inner annular surface 524 of the annular cylindrical member 522 to afirst radially outer surface 514 of the first projection 510, and asecond radially outer surface 516 of the second projection 512 of theelongated member 504 in a similar fashion to the first and secondrecessed areas, 426 and 428 of the embodiment depicted in FIG. 4. Oneskilled in the art can appreciate the features of piston 402 for theembodiment shown in FIG. 4 are apparent with the alternative embodimentdisclosed in FIG. 5.

Referring now to FIG. 7, a process flow diagram of a method ofmanufacturing a piston, as disclosed above, is illustrated in accordancewith the instant invention.

A first step 90 of the process includes providing the elongated member404 having the first radially outwardly extending projection 410 withthe first radially outer surface 414 defined by the first outer diameterD₅ at the first end 406 of the elongated member 404, and also providingthe second radially outwardly extending projection 412 with the secondradially outer surface 416 defined by the second diameter D₆substantially equal to the first outer diameter D₅ at the second end 408of the elongated member 404 (FIG. 4).

The method continues by providing, in a second step 92, the annularcylindrical member 422 having the inner annular surface 424 defined byan inner diameter D₇ (FIG. 4), which is substantially equal to the firstand second outer diameters, D₅ and D₆ of the first and second radiallyouter surfaces, 414 and 416 of the first and second projections, 410 and412 of the elongated member 404.

The method continues by allowing alternative embodiments of the piston402 to be manufactured either via a first forming step 94 and a secondforming step 96, or a first alternate step 98 and a second alternatestep 100. The first forming step 94 includes forming the firstcircumferentially extending recessed area 426 in the first radiallyouter surface 414 of the first projection 410 of the elongated member404 (FIG. 4). The second forming step 96 includes forming the secondcircumferentially extending recessed area 428 in the second radiallyouter surface 416 of the second projection 412 of the elongated member404. The first alternate step 98 includes forming the firstcircumferentially extending recessed area 550 in the first radiallyouter surface 514 of the first projection 510 of the elongated member504 (FIG. 5). The second alternate step 100 includes forming the secondcircumferentially extending recessed area 552 in the second radiallyouter surface 516 of the second projection 512 of the elongated member504 (FIG. 5). One skilled in the art can appreciate the second formingstep 96 is utilized in the embodiment employing the first forming step94 (FIG. 4), and the second alternate step 100 is utilized in thealternate embodiment employing the first alternate step 98 (FIG. 5).

As illustrated in FIG. 7, the process concludes in a final step 102. Inthe final step 102, the annular cylindrical member 422 is welded to thefirst projection 410 and the second projection 412 of the elongatedmember 404 by welding to the first and second recessed areas, 426 and428, of the first and second radially outer surfaces, 414 and 416 of thefirst and second projections, 410 and 412, respectively, of theelongated member, formed in the first and second forming steps, 94 and96, or by welding to the first and second recessed areas, 550 and 552,of the inner annular surface 524 of the annular cylindrical member 522,formed in the first and second alternate steps, 98 and 100, depending onwhether the embodiment of FIG. 4 or FIG. 5 is being manufactured. Bylimiting penetration of welding to either of the first and secondrecessed areas, 426 and 428, or the first and second recessed areas, 550and 552, any particles produced while welding the annular cylindricalmember 422 to the first and second projections, 410 and 412 of theelongated member 404 are received and contained within either of thefirst and second recessed areas, 426 and 428, or 550 and 552, andsubsequently prevented from entering the cavity 430.

In the final step 102, several welding alternatives may be utilized toweld the annular cylindrical member 422 to the first and secondprojections, 410 and 412 of the elongated member 404. These includeelectron beam welding, laser beam welding and arc welding, as forexample, in the form of tungsten inert gas welding or plasma arcwelding. One skilled in the art can appreciate that a brazing processcould also be utilized to fixedly secure the annular cylindrical member422 to the first and second projections, 410 and 412 of the elongatedmember 404.

Numerous modifications in the alternative embodiments of the inventionwill be apparent to those skilled in the art in view of the foregoingdescription. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the best mode of carrying out the invention. The details of thestructure may be varied substantially without departing from the spiritof the invention, and the exclusive use of all modifications which comewithin the scope of the appended claims is reserved.

We claim:
 1. A method of manufacturing a piston, comprising the stepsof:providing a substantially cylindrical member having a first end and asecond end; forming an open cavity in the cylindrical member extendingaxially from the second end to adjacent the first end such that thesecond end has an inner annular surface defined by an inner diameter;providing a disk having a radially outer surface defined by an outerdiameter substantially equal to the inner diameter of the inner annularsurface of the second end of the cylindrical member; forming acircumferentially extending recessed area in the radially outer surfaceof the disk; and welding the disk to the second end of the cylindricalmember by welding to the recessed area of the radially outer surface ofthe disk such that particles produced while welding the disk to thesecond end of the cylindrical member are received and contained withinthe recessed area.
 2. The method of claim 1 wherein the step of weldingthe disk to the second end of the cylindrical member further includesselecting from the group of electron beam welding, laser beam weldingand arc welding the disk to the second end of the cylindrical member. 3.A method of manufacturing a piston, comprising the steps of:providing asubstantially cylindrical member having a first end and a second end;forming an open cavity in the cylindrical member extending axially fromthe second end to adjacent the first end such that the second end has aninner annular surface defined by an inner diameter; providing a diskhaving a radially outer surface defined by an outer diametersubstantially equal to the inner diameter of the inner annular surfaceof the second end of the cylindrical member; forming a circumferentiallyextending recessed area in the radially outer surface of the disk; andbrazing the disk to the second end of the cylindrical member by brazingto the recessed area of the radially outer surface of the disk such thatexcess brazing material produced while brazing the disk to the secondend of the cylindrical member is received and contained within therecessed area.
 4. A method of manufacturing a piston, comprising thesteps of:providing a substantially cylindrical member having a first endand a second end; forming an open cavity in the cylindrical memberextending axially from the second end to adjacent the first end suchthat the second end has an inner annular surface defined by an innerdiameter; providing a disk having a radially outer surface defined by anouter diameter substantially equal to the inner diameter of the innerannular surface of the second end of the cylindrical member; forming acircumferentially extending recessed area in the inner annular surfaceof the second end of the cylindrical member; and welding the disk to thesecond end of the cylindrical member by welding to the recessed area ofthe inner annular surface of the second end of the cylindrical membersuch that particles produced while welding the disk to the second end ofthe cylindrical member are received and contained within the recessedarea.
 5. The method of claim 4 wherein the step of welding the disk tothe second end of the cylindrical member further includes selecting fromthe group of electron beam welding, laser beam welding and arc weldingthe disk to the second end of the cylindrical member.
 6. A method ofmanufacturing a piston, comprising the steps of:providing asubstantially cylindrical member having a first end and a second end;forming an open cavity in the cylindrical member extending axially fromthe second end to adjacent the first end such that the second end has aninner annular surface defined by an inner diameter; providing a diskhaving a radially outer surface defined by an outer diametersubstantially equal to the inner diameter of the inner annular surfaceof the second end of the cylindrical member; forming a circumferentiallyextending recessed area in the inner annular surface of the second endof the cylindrical member; and brazing the disk to the second end of thecylindrical member by brazing to the recessed area of the inner annularsurface of the second end of the cylindrical member such that excessbrazing material produced while brazing the disk to the second end ofthe cylindrical member is received and contained within the recessedarea.
 7. A method of manufacturing a piston, comprising the stepsof:providing an elongated member having a first radially outwardlyextending cylindrical projection with a first radially outer surfacedefined by a first outer diameter at a first end of the elongated memberand a second radially outwardly extending cylindrical projection with asecond radially outer surface defined by a second outer diametersubstantially equal to the first outer diameter at a second end of theelongated member; providing an annular cylindrical member having aninner annular surface defined by an inner diameter substantially equalto the first and second outer diameters of the first and second radiallyouter surfaces of the first and second projections of the elongatedmember; forming a first circumferentially extending recessed area in thefirst radially outer surface of the first projection of the elongatedmember; forming a second circumferentially extending recessed area inthe second radially outer surface of the second projection of theelongated member; and welding the annular cylindrical member to thefirst and second projections of the elongated member by welding to thefirst and second recessed areas of the first and second radially outersurfaces of the first and second projections of the elongated membersuch that particles produced while welding the annular cylindricalmember to the first and second projections of the elongated member arereceived and contained within the first and second recessed areas. 8.The piston of claim 7 wherein the step of welding the annularcylindrical member to the first and second projections of the elongatedmember further includes selecting from the group of electron beamwelding, laser beam welding and arc welding the annular cylindricalmember to the first and second projections of the elongated member.
 9. Amethod of manufacturing a piston, comprising the steps of:providing anelongated member having a first radially outwardly extending cylindricalprojection with a first radially outer surface defined by a first outerdiameter at a first end of the elongated member and a second radiallyoutwardly extending cylindrical projection with a second radially outersurface defined by a second outer diameter substantially equal to thefirst outer diameter at a second end of the elongated member; providingan annular cylindrical member having an inner annular surface defined byan inner diameter substantially equal to the first and second outerdiameters of the first and second radially outer surfaces of the firstand second projections of the elongated member; forming a firstcircumferentially extending recessed area in the inner annular surfaceof the annular cylindrical member opposite the first projection of theelongated member; forming a second circumferentially extending recessedarea in the inner annular surface of the annular cylindrical memberopposite the second projection of the elongated member; and welding theannular cylindrical member to the first and second projections of theelongated member by welding to the first and second recessed areas ofthe inner annular surface of the annular cylindrical member such thatparticles produced while welding the annular cylindrical member to thefirst and second projections of the elongated member are received andcontained with the first and second recessed areas.
 10. The piston ofclaim 9 wherein the step of welding the annular cylindrical member tothe first and second projections of the elongated member furtherincludes selecting from the group of electron beam welding, laser beamwelding and arc welding the annular cylindrical member to the first andsecond projections of the elongated member.